Bicarbonate-buffered dialysis solutions containing calcium ions or magnesium ions typically contain electrolytes, buffers and glucose in physiologically effective concentrations. There is a problem with dialysis solutions which also contain bicarbonate as a buffer in addition to calcium or magnesium in that under certain conditions, in particular at a comparatively high pH and at higher temperatures, carbonates may be formed which are of low solubility, which is unwanted.
Dialysis solutions having a physiological phosphate content are used in acute dialysis to regulate the phosphate balance of patients and to prevent hypophosphatemia. A medically sensible phosphate concentration is in the range from 0.65 to 1.45 mmol/L, or more specifically 0.80 to 1.25 mmol/L, based on experience from clinical application.
If a bicarbonate-buffered dialysis solution containing calcium ions or magnesium ions contains phosphate ions in addition to the bicarbonate ions, there is potentially a risk that phosphate compounds may form which are difficult to dissolve. Due to their low solubility, alkaline earth phosphate precipitations must be classified even more critically from a medical aspect than alkaline earth carbonate precipitations and should therefore be avoided.
A pH increase due to a loss of CO2 by degassing is in particular responsible for the alkaline earth carbonate precipitations and the alkaline earth phosphate precipitations. Under thermodynamic aspects, there is a maximum pH up to which the dialysis solution remains stable, i.e. up to which the named precipitations do not occur. If the pH of the dialysis solution increases under conditions of use such as by the pumping and heating at a dialysis machine or by storage, a metastable state can be achieved. If this state collapses, carbonates and/or phosphates are precipitated which are of low solubility, which can result in considerable complications in the treatment. Magnesium phosphates and calcium phosphates of low solubility in this respect represent the most critical compounds due to the low solubility in basic conditions. However, magnesium carbonate and calcium carbonate also represent critical compounds due to the poor solubility in basic conditions.
It is known from the prior art to prepare bicarbonate-buffered dialysis solutions containing calcium ions or magnesium ions in the form of individual solutions which are received in a dual-chamber bag. This can be realized for solutions which furthermore contain phosphate. A ready-to-use dialysis solution is obtained by mixing the two chamber contents. A separate storage of calcium, on the one hand, and of carbonate or phosphate, on the other hand, and thus an increased stability in the storage of the dialysis solution, can be achieved by the provision of the individual solutions in a dual-chamber bag. It is further known from the prior art to manufacture the bag film from a barrier film to counteract the escape of CO2 and thus the increase in the pH in the individual solution containing bicarbonate and optionally phosphate. Nevertheless, despite this special packaging, the pH of the dialysis solution containing bicarbonate and optionally phosphate increases over the storage time, which has the consequence that on the mixing of the two individual solutions, the pH of the mixed solution, i.e. of the finished dialysis solution, is likewise increased before its use. To avoid precipitations in the mixing or on the use at the dialysis machine, it is best to ensure that the pH of the dialysis solution containing bicarbonate and optionally phosphate and the pH of the mixture manufactured from the individual solutions lie within a relatively narrow framework.
This disclosure provides a bicarbonate-buffered dialysis solution which contains calcium ions or magnesium ions and which generally has a physiological phosphate content such that the probability for the occurrence of precipitations is reduced with respect to known solutions.